Vented fuse module for underground power cable system

ABSTRACT

A multi-part, separable fuse module having a relatively flexible pair of overlapping surfaces that afford a water-tight seal between the parts of the module is provided with gas-venting passage-ways through predetermined portions of these overlapping surfaces in order to enable high pressure gases to temporarily open the passageways and escape from the interior of the module, without allowing water to enter the module. In combination with the fuse module, the invention comprises a rigid clamping member mounted over the relatively separable parts of the module to maintain them in fixed relationship during a gas-venting operation.

[ 1 July 18,1972

United States Patent Boliver [s4] VENTED FUSE MODULE FOR ...l74/73 R X...l74/73 R X Simpson et al.....................337I205 X 1,874,9488/1932 Fogal UNDERGROUND POWER CABLE 7 5/1 7 Tordoff.... SYSTE 3,307,1372/1967 Tordoff...........

M 2,785,319 3/1957 [72] lnventor:

Vincent J. Deliver, Pittsfield, Mass.

General Electric Company April 26, 1971 Primary Examiner-Bernard A.Gilheany Assistant Examiner-Dewitt M. Morgan [73] Assignee:

[22] Filed:

Anomey-Vaie P. Myles, Francis X. Doyle, Frank L. Neuhauser, Oscar B.Waddell and Joseph B. Forman [2|] Appl. No.:

ABSTRACT A multi-part, separable fuse module having a relatively flexi-[52] US. Cl. ....337/201, 174/73 R, 337/203,

339/117 R ble pair of overlapping surfaces that afford a water-tightseal .l-I0lh 85/02, HOlh 85/54, HOlr 13/52 between the parts of themodule is provided with gas-venting [51] lnt.Cl................ [58]Field otsearch..l..............174/73 R; 337/201, 203, 205, p g y h gh prm n portions of these over- 337/249, 250, 272, 28]; 339/11 l. 112 R 17R lapping surfaces in order to enable high pressure gases to temporarilyopen the passageways and escape from the interior of the module, withoutallowing water to enter the module. in combination with the fuse module,the invention comprises a rigid clamping member mounted over therelatively separable parts of the module to maintain them in fixedrelationship dur- [56] References Cited UNITED STATES PATENTS H as m m H3 o m m r M m. C O 6 g n U n e V m g a g .m 9 04 22 l/ 77 33 33 Ta "t hen m A] 09 76 99 11 I, 56 5s 22 31 5 33 VEN'IED FUSE MODULE FORUNDERGROUND POWER CABLE SYSTEM BACKGROUND OF THE INVENTION The inventionis related to underground power distribution systems, and moreparticularly to a fuse module for use on such systems. The fuse moduleof the invention incorporates means that are operable to vent highpressure gases therefrom, without destroying the water-tight integrityof the module.

Prior to the present invention, it was well known in the field ofunderground electric power distribution to utilize molded, modular-typeelectric cable terminations to inter-connect, or terminate, theconductors of the system. Moreover, suitable modules have already beenmanufactured for mounting system components, such as current limitingfuses, in operating relationship with the power conductors of suchsystems. An example of such prior art underground fuse modules isdisclosed in US. Pat. No. 3,5l3,425-Arndt, which issued May l9, I970 andis assigned to the assignee of the present invention.

It has been found that such prior art types of underground fuse modulesare completely satisfactory for normal use with cartridge type fuses ofa kind that do not evolve substantial amounts of gas during a circuitinterrupting operation. However, when fuses utilizing gas-evolving,arc-extinguishing materials are utilized in such prior art fusedmodules, there is a substantial degree of risk that a fuse circuitinterrupting operation will result in the fuse module being forced toseparate or open. Of course, such a separation could cause the powersystem to be grounded if the module happens to be submerged in water,which would rush into contact with the energized power cable terminatedwithin the module. Accordingly, since gas-evolving power fuses willprobably be used on many of the high current power distribution linesbeing placed in use, it is desireable to provide a suitable means forassuring that such fuses can be safely used in underground distributionsystem fuse modules.

One solution proposed for the foregoing problem required the use of aseparable fuse module in which the power cable termination contactswould be mounted in bell-shaped cavities. In placing such a module inoperation on an underground power system, care would be taken to mountthe module in a vertical position such that the element of the modulecontaining a contact that terminates the hot side of the system would bein an inverted position. Consequently, if the fuse module becameseparated during a fuse interrupting operation, the inverted cavitywould act like a divers bell to prevent water from contacting theenergized side of the power system. While such a fuse module design istheoretically possible, it has been found to have many practicaldrawbacks in actual field application. Perhaps the most severe of thesedrawbacks is that a short circuit to ground might still occur on a highvoltage distribution system due to current arcing-over the air gapbetween the energized terminal and the water level allowed to developwithin the fuse module when the fuse fails.

OBJECTS OF THE INVENTION A primary object of the present invention is toprovide an underground power distribution system fuse module, whichovercomes the disadvantages and shortcomings of prior art fuse modulesnoted above.

Another object of the invention is to provide a fuse module having gasventing means that enable gas to be rapidly and automatically ventedfrom the module in response to high gas pressures being developed withinit. Such gas venting occurs without allowing water to enter the fusemodule.

A further objective of the invention is to provide a multipart fusemodule in combination with clamping means for preventing axialseparation of component parts of the module during a gas ventingoperation.

A still further object of the invention is to provide a multipart fusemodule having a pair of relatively movable, molded elastomeric housingcomponents that are adapted to separate in response to the developmentof high gas pressure within the module, thereby to serve as aclapper-type valve that exhausts gas from the module without allowingwater to enter it.

Additional objects and advantages of the invention will become apparentto those skilled in the art from the disclosure that follows, taken inconjunction with the accompanying drawings.

SUMMARY OF THE INVENTION A multi-part, molded, elastomeric fuse modulefor an underground electric power distribution system is provided withventing means for exhausting high pressure gases from the module withoutallowing water to enter it. The separate parts of the module are mountedin operating position in a manner such that at least a portion of theirrespective juxtaposed end surfaces overlap in water-tight sealingrelationship. One or more gas venting passageways are formed through apredetermined portion of the overlapping end of the surfaces. Thepassageway or passageways are operable to vent gases from the interiorof the module without allowing water into the module, due to the sealingrelationship that is maintained between its respective parts during agas venting operation. In one embodiment of the invention, maintenanceof this sealing relationship is assured by the provision of a clampingmember, in combination with the fuse module, to prevent relativemovement in an axial direction between the parts of the fuse module. Inaddition, the innermost of the overlapping module surfaces is maderelatively rigid with respect to the outer surface, therefore, when highpressure gases are developed within the module the outer surface istemporarily expanded radially away from the inner surface to afford aclapper valve type of operation between the two surfaces. This valveaction allows gases to be vented from the fuse module through theaforementioned passageways.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation view,partly in cross section, of an underground electric power fuse moduleconstructed pursuant to the teaching of the present invention, and shownwith some of its components in a partly separated position.

FIG. 2 is a side elevation view of the fuse module illustrated in FIG.1, showing the component parts of the fuse module in assembled position,and illustrating a clamping member in combination with the fuse modulepursuant to a teaching of the present invention.

FIG. 3 is a perspective view of the clamping member illustrated in FIG.2 of the drawing,

DESCRIPTION OF SOME PREFERRED EMBODIMENTS OF THE INVENTION Referring nowto FIG. I of the drawing, it will be seen that there is shown athree-part fuse module that is adapted for use with a high voltageelectric power distribution system. The fuse module 1 comprises a firstconductor combination module 2, a second conductor termination module 3,and a fuse shielding module 4. The first and second conductor modules, 2and 3, are substantially identical in construction; therefore, in orderto explain the present invention only the module 3 will be described indetail herein. All of the modules 2-4 are forms of molded, resilient,insulating material that may be a suitable, conventional elastomericcompound similar to that referred to in the above-mentioned Arndtpatent, or any other suitable, relatively flexible insulating material.As shown in the cross section view of module 3 the major portion thereofcomprises a body of insulating material 5. A coating 6 of electricallyconductive, sulphur-cured elastomeric material is bonded to the outersurface of the module 3 by being sprayed, or dipped-formed thereon.Mounted within the module 3 is an electrical contact member 7 formed ofaluminum. A fluted angular contact 8 is screwed into the contact member7 to be retained in position, as shown.

It will be understood that during normal assembly, the contact 7 iscrimped onto the conductor of insulated electric power cable. The cable9 and contact member 7 are then forced into an axial passageway in themodule 3 to the position shown in FIG. 1. Next. the fluted terminal 8 isscrewed into the member 7 to form the assembly as shown. In order toshield the irregular surfaces of this combination contact assembly, amolded layer of conductive elastomeric material 10 is bonded to theinner surface of the body of insulating material of module 3, as shown.It will be noted that one end of the conductive sleeve terminates in anannular metal spring II that is mounted near the small diameter end of afrustoconical surface 12, that extends from the spring II to an annularlip portion 13 adjacent its large diameter end. As shown in FIG. I, thelip portion 13 protrudes inwardly from the large diameter end of thefrusto-conical surface 12 and it forms a relatively sharp angle(slightly less than 90) with that surface, to afford a latching functionthat will be explained hereinafier.

The module 3 also includes an integral boss 14 on which there is mounteda ring 15, or other loop configuration, that is adapted to receive amanually operated hot stick with which the module 3 can be manipulatedwhen the electric power system on which it is mounted is de-energized.

Fuse shielding module 4 comprises a relatively rigid wall member 17 onwhich a layer of electrically semi-conductive material I8 is applied.Over the material 18, a layer of elastomeric dielectric material 16 ismolded. In order to provide a continuous ground coating for themulti-part module 1, the outer surface of fuse shielding module 4 iscoated with an electrically conductive elastomeric coating 19 thatextends along its general cylindrical central portion. Both ends of fuseshielding module 4 are substantially identical in shape and are formedas frusto-conical end surfaces 20,20. As shown in FIG. 1 thesefrusto-conical end surfaces 20,20 terminate in generally annular ridgeportions 21,2l In other embodiments of the invention the fuse module (4)may be formed of relatively rigid insulating material, so that a wallmember, such as member 17 is not required. Of course, in such anembodiment. a semiconductive layer (l8) and a conductive coating I9should still be utilized. It will be understood that the generallyannular ridge portion 21,21 are latched in position with respect totermination modules 2 and 3 by their engagement with the lips 13 and 13'when the modules 2, 3 and 4 are assembled in operating position. Also,it will be understood that a cartridge type fuse, one terminal 22 ofwhich is shown in FIG. I, is normally mounted within the module 1 whenit is thus assembled in operating position in a power distributionsystem, thereby to complete a conductive circuit between the powerconductor 9 and a second conductor 23 that is mounted in module 2. Thefeatures of fuse module 1, as described thus far, are generally known inthe art, and they have been substantially described in the aboveidentified Arndt patent. The characteristic features of the inventiondisclosed and claimed herein, as embodied in the structure illustratedin FIG. 1, comprise gas venting means for releasing gas under pressurefrom the interior of the fuse module 1. In this embodiment of theinvention, the gas venting means are in the form of a plurality ofpassageways defined through the annular lip portions l3, 13' of theconductor termination module 2 and 3. Two of these passageways, 24 and25, are shown in the lip portion 13 of module 3, at equally-spaced-apartpoints thereon. It will be understood that two additional passageways(not shown) are also positioned in the other half of the module 3 sothat there are a total of four equally-spaced-apart passageways aroundthe periphery of the annularly shaped lip portion 13. In like manner, anumber of passageways are formed in the lip portion 13' of conductortermination module 2, although these passageways are not visible in FIG.I. It should be understood that in some applications a single gasventingpassageway will be suitable to afford the objectives of the invention;however, for present day power distribution systems it has been foundthat a plurality of passageways (24, 25, etc.) spaced at equallyseparated distances around the periphery of the lip portions 13 and 13'are preferable. Moreover, it has been found that these passagewaysshould each have a width of at least one-sixteenth of an inch over theirentire length. This width affords ample venting capability for the typeof gas evolving fuses currently in use.

In the operation of this form of the invention when gas is releasedunder pressure within the fuse module 1, the rigid wall member 17 offuse shielding module 4 prevents its frustoconical surface 20 from beingdistorted radially outward. On the other hand, the gas pressure isoperative to force the frusto-conical surface 12 of conductortermination module 3 outward, thereby to make it operate as aclapper-type valve to temporarily lift the lip portion 13 radiallyoutward with respect to the annular ridge 2!, so that gas is ventedthrough the passageways (24 and 25). In the preferred form of theinvention, the passageways (24 and 25) are generally triangular in crosssection. This configuration of these passageways allows a progressivelygreater exposure to the outer atmosphere as the lip portion 13 movesradially outward, so that more gas can be vented in proportion to suchoutward movement.

In many field applications, the latching effect between lip portions 13and I3 and ridge portions 21 and 21' is sufficient to prevent theseparate component modules of fuse module I from being separated duringa gas-venting operation. However, it has been found that for other,higher interrupting current applications, additional means must beprovided to assure the water-tight integrity of the seal formed betweenthe frustoconical surfaces (12 and 20) during a gas-venting operation.One embodiment of such an arrangement will now be described in detailwith reference to FIG. 2 of the drawing.

There is shown in FIG. 2, a fuse module 1 that is identical to the fusemodule 1 that is illustrated in FIG. I. Accordingly, like referencenumerals are used in FIG. 2 to designate similar component parts. Thefuse module I is shown with cable termination modules 2 and 3 mounted inassembled, operating position on cable shielding module 4. In thisembodiment of the invention a relatively rigid clamping member 26 isremovably mounted over the outside of the first termination module 2 andthe second termination module 3. The clamping member 26 is generallyU-shaped and is formed of stainless steel bar stock approximatelythree-sixteenths of an inch thick and 2 /4 inches wide. As seen moreclearly in FIG. 3, the clamping member 26 includes means defining a pairof generally U-shaped slots, 27 and 28, in each of its opposite ends.The U-shaped slots 27 and 28 are adapted to cooperate, respectively,with the boss elements 14 and 14' of the first and second terminationmodules 3 and 2. Specifically, the U shaped slots 27 and 28 serve tomaintain the clamping member 26 mounted in operating position, as shownin FIG. 2, over the respective bosses l4, 14' on said modules 2 and 3.

In operation, the embodiment of the invention depicted in FIG. 2functions generally in the same manner as the embodiment of theinvention illustrated in FIG. I but, in addition, the clamping member 26is operable to prevent relative movement between the modules 2-4 in anaxial direction. Thus, clamping member 26 assures maintenance of awater-tight sealing relationship between the respective abutting frustoconical surfaces 12-20 and l220' on the ends of fuse shielding module 4and modules 2 and 3.

From the foregoing description of the invention it will be apparent tothose skilled in the art that various modifications and alternativeembodiments of it may be used to afford the unique advantages inherentin its teaching. For example, it will be apparent that the inventionwill perform equally well on a two-part fuse module. In order to brieflyexplain such an application, reference is again made to FIG. 1 of thedrawing. It should be obvious that, if desired, the modules 2 and 4could be molded together as a single first conductor termination module(2-4) which would have a generally frusto-conical end surface (20),which still be adapted to cooperate with the frusto-conical (l2) of asecond module 3, to form a watertight seal around the fuse-holdingcavity formed in the module (2-4), as described above. In otherrespects, the construction of such a more generally unitary fuse module1 could be similar to the embodiment of the invention described above,initially, with reference to FIG. 1. Also, a clamping member, such asthe clamping member 26, could be used to hold a twopart fuse module inoperating water-tight relationship as explained above with reference tothe embodiment of the invention depicted in FIG. 2.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A three-part fuse module for high voltage electric power conductorscomprising; first and second conductor termination modules and a fuseshielding module, said first and second modules being formed of molded,resilient insulating material and having respectively, generallyfrusto-conical end surfaces that form water-tight, voltage grading sealswith opposed, generally frusto-conical end surfaces of said fuseshielding module, when coupled in operating position therewith, each ofsaid first and second modules having an annular lip portion protrudinginwardly from the larger diameter section of their respective endsurfaces, said shielding module having a pair of generally annular ridgeportions that respectively engage said annular lip portions, thereby tolatch said modules together, and gas venting means for releasing gasunder pressure from the interior of said fuse module, said gas ventingmeans being disposed adjacent said lip portions and being operable toprevent water from entering the fuse module while gas is ventedtherefrom, and said gas venting means being formed to define a pluralityof spaced-apart passageways through the annular lip portion of at leastone of said conductor termination modules.

2. The invention defined in claim 1 wherein each of said modules isformed of molded resilient insulating material, said fuse shieldingmodule including a relatively rigid wall member that is effective toprevent the generally annular ridge portions thereof from being forcedradially outward when gas pressure is developed within the fuse moduleby failure of a gasgenerating fuse mounted therein, whereby such gaspressure is eflective to temporarily separate the water-tight sealsbetween said modules due to the outward radial movement of thefrusto-conical surfaces of said first and second modules responsive togas pressure, thereby to vent gas through said passageways.

3. The invention defined in claim 1 wherein said first and secondtermination modules are formed of resilient insulating material, andsaid fuse module is formed of a rigid insulating material, whereby gaspressure developed by a fuse failure is effective to temporarilyseparate the water-tight seals between said modules due to the outwardradial movement of the frusto-conical surfaces of said first and secondmodules responsive to gas pressure, thereby to vent gas through saidpassageways.

4. The invention defined in claim I including a relatively rigidclamping member removably mounted over the outside of said first andsecond conductor termination modules, said clamping member beingoperable to prevent relative movement between said modules in an axialdirection while being freely movable with said modules as an assembly,thereby assun'ng maintenance of a water-tight sealing relationshipbetween the first and second modules and said fuse shielding moduleduring a gas venting operation even when said modules are moved from afixed position during such an operation.

5. The invention defined in claim 4 wherein said clamping member isgenerally U-shaped in configuration and includes means defining agenerally U-shaped slot in each end thereof, said U-shaped slots beingadapted to cooperate, respectively, with boss elements on said first andsecond modules, thereby to maintain the clamping member in operatingposition with respect to said modules.

6. A three-part fuse fuse module for high voltage electric powerconductors comprising; first and second conductor termination modulesand a fuse shielding module, said first and second modules being formedof molded, resilient insulatin material and having respectively,generally frusto-conlcal en surfaces that form water-tight, voltagegrading seals with opposed, generally frustoconical end surfaces of saidfuse shielding module, when coupled in operating position therewith,each of said first and second modules having an annular lip portionprotruding inwardly from the larger diameter section of their respectiveend surfaces, said shielding module having a pair of generally annularridge portions that respectively engage said annular lip portions,thereby to latch said modules together, and gas venting means forreleasing gas under pressure from the interior of said fuse module, saidgas venting means being disposed adjacent said lip portions and beingoperable to prevent water from entering the fuse module while gas isvented therefrom, and including four equally spaced-apart passagewaysformed in each of said annular lip portions, each of said passagewaysbeing at least onesixteenth inch wide over its entire length,

* 1 I t I

1. A three-part fuse module for high voltage electric power conductorscomprising; first and second conductor termination modules and a fuseshielding module, said first and second modules being formed of molded,resilient insulating material and having respectively, generallyfrusto-conical end surfaces that form water-tight, voltage grading sealswith opposed, generally frusto-conical end surfaces of said fuseshielding module, when coupled in operating position therewith, each ofsaid first and second modules having an annular lip portion protrudinginwardly from the larger diameter section of their respective endsurfaces, said shielding module having a pair of generally annular ridgeportions that respectively engage said annular lip portions, thereby tolatch said modules together, and gas venting means for releasing gasunder pressure from the interior of said fuse module, said gas ventingmeans being disposed adjacent said lip portions and being operable toprevent water from entering the fuse module while gas is ventedtherefrom, and said gas venting means being formed to define a pluralityof spaced-apart passageways through the annular lip portion of at leastone of said conductor termination modules.
 2. The invention defined inclaim 1 wherein each of said modules is formed of molded resilientinsulating material, said fuse shielding module includiNg a relativelyrigid wall member that is effective to prevent the generally annularridge portions thereof from being forced radially outward when gaspressure is developed within the fuse module by failure of agas-generating fuse mounted therein, whereby such gas pressure iseffective to temporarily separate the water-tight seals between saidmodules due to the outward radial movement of the frusto-conicalsurfaces of said first and second modules responsive to gas pressure,thereby to vent gas through said passageways.
 3. The invention definedin claim 1 wherein said first and second termination modules are formedof resilient insulating material, and said fuse module is formed of arigid insulating material, whereby gas pressure developed by a fusefailure is effective to temporarily separate the water-tight sealsbetween said modules due to the outward radial movement of thefrusto-conical surfaces of said first and second modules responsive togas pressure, thereby to vent gas through said passageways.
 4. Theinvention defined in claim 1 including a relatively rigid clampingmember removably mounted over the outside of said first and secondconductor termination modules, said clamping member being operable toprevent relative movement between said modules in an axial directionwhile being freely movable with said modules as an assembly, therebyassuring maintenance of a water-tight sealing relationship between thefirst and second modules and said fuse shielding module during a gasventing operation even when said modules are moved from a fixed positionduring such an operation.
 5. The invention defined in claim 4 whereinsaid clamping member is generally U-shaped in configuration and includesmeans defining a generally U-shaped slot in each end thereof, saidU-shaped slots being adapted to cooperate, respectively, with bosselements on said first and second modules, thereby to maintain theclamping member in operating position with respect to said modules.
 6. Athree-part fuse fuse module for high voltage electric power conductorscomprising; first and second conductor termination modules and a fuseshielding module, said first and second modules being formed of molded,resilient insulating material and having respectively, generallyfrusto-conical end surfaces that form water-tight, voltage grading sealswith opposed, generally frusto-conical end surfaces of said fuseshielding module, when coupled in operating position therewith, each ofsaid first and second modules having an annular lip portion protrudinginwardly from the larger diameter section of their respective endsurfaces, said shielding module having a pair of generally annular ridgeportions that respectively engage said annular lip portions, thereby tolatch said modules together, and gas venting means for releasing gasunder pressure from the interior of said fuse module, said gas ventingmeans being disposed adjacent said lip portions and being operable toprevent water from entering the fuse module while gas is ventedtherefrom, and including four equally spaced-apart passageways formed ineach of said annular lip portions, each of said passageways being atleast one-sixteenth inch wide over its entire length.